Saw chain



April 16, 19 57 R. c. BERNARD ErAL 2,788,811

SAW CHAIN I Filed Jan. 12, 1955 v 2 Sheets-Sheet 1 INVENTORS .Rn mouo. CLIFTON BERNBRD' LEON EDEL.SN

ATTORNEY p 1957 R. c. BERNARD ETAL 2,788,811

saw CHAIN Filed Jan. 12, 1955 2 Sheets-Sheet 2 INVENTORS RAYMOND cuFroN BERNHRD 9 BY H EDELSOH ATTORNEY Unite rates atent SAW CHAIN Raymond Clifton Bernard, Coatesville, and Leon Edelson, Elkins Park, Pa., assignors to L-M Manufacturing Company, Inc., Coatesville, Pa., a corporation of Fennsylvania Application January 12, 1955, Serial No. 481,292

Claims. (Cl. 143-135) This invention relates generally to chainsaws and is concerned more particularly with improvements in the design of the links making up the saw chain and with the wood cutting elements that are incorporated with some of the links.

In the operation of a chain saw for cutting lumber, the wood which immediately underlies the saw chain is separated from the main body of the wood in layers by the cutting elements of the saw chain, which elements progressively penetrate deeper into the main body of the wood as each successive layer is separated. When sawing in the direction of the wood grain with known saw chains, the layers are separated from the main body of the wood as the cutting elements advance at an angle to the direction of the wood grain, shearing off (as distinguished from cutting under or wedging between) the wood fibers, in consequence of which all of the wood fibers in a layer extend through the layer in the direction of its thickness. On the other hand, when sawing crossgrain, with known saw chains, at least a substantial part, if not all, of each layer is separated from the main body of the wood as the cutting elements advance each in a plane parallel to the wood grain, cutting under or wedging between (as distinguished from shearing off) the wood fibers, which extend across the layer in the direction of its width. While thecutting elements encounter a considerable amount of resistance to their advance when they work through the wood by shearing ofi the wood fibers, they encounter much more resistance to their advance when they work through the wood by cutting under or ,wedging between the wood fibers, and one disadvantage of the prior art saw chains is that their cutting elements are designed and arranged so that, when sawing cross-grain, separation of a layer from the main body of the wood is not effected entirely by the aforementioned shearing action, in consequence of which the cutting operation is slower, less smooth and more power consuming.

Accordingly, a principal object of the present invention is to provide an improved form of cutting elements for wood sawing chains operative, when cutting crossgrain, to cut a kerf progressively deeper entirely by shearing cuts which separate from the main body of the wood, in successive layers, the wood fiber tips exposed at the bottom of the kerf.

Another object of the present invention is to design right'and left hand cutting elements and to space the same along the chain alternately at opposite sides thereof to cut respectively along intersecting planes and to conjointly form thereby a kerf the bottom of which is V-shaped in transverse cross-section, the depth of the kerf being greatest midway between the sidewalls of the kert'.

Still another object of the present invention is to provide the saw chain aforesaid with depth gauge links spaced along the saw chain for gauging the depth of the shearing cuts made by the cutting elements and located in the median plane of the saw chain for travel in con- Patented Apr. 16, 1957 tact with the bottom of the saw kerf along the line of maximum depth, the sloping kerf bottom portions on opposite sides of the said line of travel'being operative to secure the depth gauge links and the saw chain as a whole against lateral movement and to assure straight line travel so as to reduce any tendency for the saw chain to bind in the kerf.

Another important object of the present invention is to provide a saw chain arranged to form a kerf the opposite side bottom portions of which are separated from the main body of the wood respectively by the right and left hand cutting elements aforesaid, each cutting element being operative simultaneously to longitudinally score the bottom of the kerf so that the adjoining kerf bottom portion may be separated from the main body of the wood by the next succeeding cutting element without ripping or tearing of the wood.

Still another important object of the present invention is to provide the saw chain with cutting elements shaped to favor detachment of debris therefrom after the same is expelled from the kerf and before it can re-enter the kert and aggravate any tendency for the saw chain to choke up with debris and bind in the kerf.

A further object of the present invention is to provide an improved form of cutting elements for wood cutting chains that makes possible a cutting operation that is smoother and faster and requires less power to drive the saw.

And a further object of the present invention is to provide a saw chain and a sprocket therefor, the latter having an odd number of teeth and the saw chain having sprocket engaging links operative to engage alternate sprocket teeth, odd number teeth and even numbered teeth of the'sprocket being engaged during alternate revolutions of the sprocket so as to prolong the life of the sprocket.

Other objects and advantages of the present invention will appear more fully hereinafter, it being understood that said invention consists substantially in the combination, construction, location and general arrangement of parts, all as described in detail in the following specification, as shown in the accompanying drawings and as fully pointed outin the appended claims.

In the accompanying drawings:

Figure 1 is a side elevation of a saw chain embodying the present invention;

Figure 2 is a bottom view of the saw chain shown in Figure 1;

Figure 3 is a side elevation of the saw chain shown in Figure 1 trained about a driving sprocket and a saw bar;

Figure 4 is a perspective view of the cutting element of the present invention;

Figure 5 is a side elevation of the cutting element shown'in Figure 4;

Figure 6 is a top view of the cutting element shown in Figure 5;

Figure 7 is a section on the line "77 of Figure 5;

Figure 8 is a rear view of the cutting element shown in Figure 5;

Figure 9 is a horizontal section looking down into a saw kerf formed by the saw chain and taken through the cutting elements and the depth gauge links; and

Figures 10, 11 and 12 are vertical sections on lines 1010, 11-41 and 12 12 of Figure 9.

Referring to the drawings, and particularly to Figures 1, 2 and 3, the saw chain of the present invention cornprises a plurality of links 10 and 11 disposed in the median plane of the chain and positioned alternately in longitudinally spaced relation. The links 10 are each provided with a depth gauge portion 12 which extends from the outer narrow edge of the main body part of the link a in outward continuation thereof, and the links 11 are each provided with a sprocket engaging portion 13 which extends from the inner narrow edge of the main body part ofthe link 11 in inward continuation thereof. The depth gauge and sprocket engaging portions 12 and13 are disposed in the median plane of the chain. Referring particularly to Figure 3, when the sprocket engaging portion 13 is fully engaged with a tooth 14 of a driving sprocket 15, the rear edge 16 of the sprocket engaging portion 13 slopes at an angle that corresponds to the angle of the tooth face, as shown. It will be understood that the sprocket engaging portions 13 of the links 11 travel Within the groove of a saw bar 16 The links 10 and 11 are pivotally joined together by means of pairs' of oppositely disposed side plates 17 and 18. The side plates 17 are identical with each other. The side plates 18 are provided with blade body or cutting tooth parts, and ,alternate side plates 18 are of right and left hand configuration for reasons'which appear hereinafter. In the description which follows, only one of the cutting teeth will be described in detail, the description being fully applicable in all respects to both right and left hand side plates 18.

Referring particularly to Figures 4 through 8, the side plate 18, which has the blade body or cutting tooth, will be described in greater detail. The side plate 18 may be formed from a sheet metal stamping, the cutting tooth being integral with the trailing portion of the side plate 18 and being V-shaped in cross-section. A shank portion 19 extends from the outer narrow edge 'of the main body part of the link 18 along one leg of the V, and a toe portion 20 extends from the shank portion 19 along the other leg of the V at a slightly obtuse angle relative to the shank portion 19, the shank and toe portions 19 and 20 being disposed relative to the median plane of the chain respectivelyat angles that are approximately equal, thus placing the toe portion 20 at an acute angle relative to said median plane of approximately forty-five degrees, From point 21 on the leading edge of the cutting tooth where the shank and toe portions 19 and 20 meet, the

toe portion of the leading edge extendsrearwardly and.

outwardly and at an angle relative to the median plane of the chain, and the shank portion of the leading edge curves inwardly and rearwardly and then sweeps forwardly to merge with the narrow outer edge of the main body part of the link 18. The leading edge of the cutting tooth is suitably beveled to provide a continuous chisel or cutting edge 22 which extends all along the leading edge of the toe portion 26. In addition, the longitudinally extending side edge of the toe portion 20 projects a short distance beyondthe median plane of the chain and is suitably beveled to provide a chisel edge 25. Along the line of juncture of the beveled surfaces of the chisel edges 22 and there is thus formed a sharp edge 25, and where the latter meets the chisel edges 22 and 25 there is formed a sharp point 25".

. Referring particularly to Figure 5,-the line of juncture of the main body of the link with the shank portion 19 and the .line of juncture of the latter with the toe portion 20 incline slightly to the rear and inwardly. Referring particularly to Figure 6, in which the line 23 represents the side Wall of the saw kerf in the wood, the line of juncture of the shank portion 19 with the toe portion 20 is raked rearwardly and toward the median plane of the chain, the angle of rake being indicated at 24. Moreover, refening particularly to Figure 5, in which the line 24 represents the bottom of the saw kerf in the wood, the chisel edge 25 is raked to the rear and inwardly, the angle of rake being indicated at 26.

An important feature of the present invention resides.

V fits snugly against the surface of the file. The edgeof the toe portion 20 will be hollow ground due to the curvature of the surface of the file; In this connection, it will be noted that in the operation of the chain saw any sharpening of the leading edge of the shank 19 is merely incidental to the sharpening of the toe 20. In fact, the leading edge of the shank 19 may be set back from the cutting edge 22 so that the latter projects freely in ad-' vance of the shank and thus may be ground to a sharp edge by a file or other sharpening tool which is entirely free of contact with the shank 19. 7

Referring particularly to Figures 10, 11 and 12, a pair of cutting teeth are shown progressing along the bottom of a saw kerf having parallel side Walls 2323 and a V shaped bottom designated 28. The cutting tooth-on the left hand side is in leading position, and the cutting tooth on the right hand side is in trailing position. The chisel edge 22 of the leading cutting tooth cuts along a plane designated.Z-Z, and simultaneously the sharp point 25 scores the bottom of the saw kerf, the sharp edge 25 and the contiguous portion of the cutting'edge 22 cutting into the main body of the wood respectively along a plane designated Y-Y and along the plane ZZ. In the meantime, the chisel edge 22 of the trailing cutting tooth cuts along a plane designated X'X (lower than the plane Z-Z) and thereby separates from the main body of the wood a layer designated '30 on the right hand side of the saw kerf. Simultaneously the sharp point 25 scores the bottom of the saw kerf, the sharp edge 25 and the contiguous portion of the cutting edge 22 cutting into the main body of the wood respectively along a plane designated W-W and the plane 'XX. Separation of the layer of wood 30 from the main body of the wood is effected eonjointly by the scoring action of the leading tooth and the cutting action of the trailing tooth, without any ripping or tearing of the wood;

It will be understood, of course, that each cutting tooth functions as a trailing tooth with respect to the opposite hand cutting tooth immediately in advance of it and as a leading tooth with respect to theopposite hand cutting tooth immediately following it, and that layers of Wood are separated from the main body of the 'wood alternately on opposite sides of the saw kerf inthe samemanner as just described for separating the layer 30.

The chisel edges 22of the right and left hand cutting teeth eonjointly extend continuously fully across the bottom of the saw kerf, and when the saw is working crossa grain the chisel edges 22. advance 'at an angle to the grain of the wood. As a result, the separation of a layer from ing movement would be effectively resisted by reason of i the depth gauge portions being supported against such shifting movement by the sloping portions of the'kerf bottom respectively on opposite sides of the depth gauge portions 12. This feature greatly enhances the stability of the saw chain and correspondingly reduces the tendency for the saw chain to bind in the kerf. The depth gauge portions 12 and the cutting teeth coact to carry debris along the saw kerf and to expel the same from one end thereof, and the cutting teeth, by reason of being V-shaped, are free from any projections to which the debris may readily adhere. The debris is readily thrown clear of the saw chain immediately after it is expelled from the saw kerf and before it can be carried around the saw bar to reenter the kerf and aggravate any tendency for the saw chain to choke up with debris and bind in the saw kerf.

Referring to Figure 3, the teeth 14 of the driving sprocket 15 are odd in number, and the sprocket engaging portions 13 of the saw chain are uniformly spaced apart a distance .suflicient for engaging only alternate sprocket teeth 14. The even numbered teeth 14, therefore, are engaged by the sprocket engaging portions 13 during one revolution of the sprocket 15, while the odd numbered teeth 14 are engaged during the next revolution, in consequence of which the life of the sprocket is prolonged. In this connection, it will be observed that in any position of the driving sprocket 15, at least two teeth 14 are engaged with sprocket engaging portions 13.

The chain saw of the present invention not only makes possible a smoother and less power consuming cutting operation, but additionally makes possible a faster cutting operation. Whereas with presently known saws the bite of the cutters normally ranges between 25 to 35 thousandths of an inch, with a maximum of 50 thousandths of an inch, the cutting teeth of the saw chain of the present invention are normally capable of biting into the wood to a depth ranging between 50 and 100 thousandths of an inch, which, of course, heavily favors a rapid cutting operation. In this connection, it will be understood that the distance between the points of intersection of the planes XX and Y-Y respectively with the median plane of the saw chain, which is the vertical depth of the cut, depends largely upon the pressure with which the chain saw is brought to bear upon the work.

It will be understood, of course, that the present invention is susceptible of various changes and modifications which may be made from time to time without involving any departu e from the general principles or real spirit thereof. Accordingly, it is intended to claim the same broadly, as well as specifically, as indicated in the appended claims.

What is claimed as new and useful is:

1. In an elongate saw chain comprising a plurality of articulately interconnected links, said chain having substantially parallel side planes defining inwardly therebetween a basic transverse dimension of the chain, and having a median plane substantially equally spaced from and substantially parallel to said side planes, and at least some of said links carrying cutters depending therefrom; the improvement wherein each cutter comprises: a member providing a cutting edge, said edge being the leading cutting edge for the cutter, said edge lying throughout its extent in a flat plane, said flat plane being parallel with the longitudinal axis of the chain and forming an acute angle of approximately forty-five degrees with said median plane, said edge extending at least between a point outside one of said side planes and a point inwardly thereof on said median plane, said edge defining the entire transverse cutting extent of the cutter, and means confined inwardly of the first point securing the cutter to a link.

2. In a saw chain as defined in claim 1, said edge extending between said point outside one of said side planes and a point inwardly thereof to the opposite side of said median plane.

3. In a saw chain as defined in claim 2, wherein said securing means comprises a shank portion integrally secured at one end thereof to said cutter member and extending inwardly from said outside point, the opposite end of said shank portion being integrally secured to said link.

4. A cutter link means for a saw chain, comprising a planar link member having two opposite sides to either side of a median plane through said link member, said link member having an axis adapted to extend in the direction of the longitudinal axis of the chain, a cutter member depending from the link member, said cutter member having an element providing a cutting edge, said edge being the leading cutting edge for the cutter member, said edge lying throughout its extent in a flat plane, said fiat plane being parallel with said link member axis and forming an acute angle of approximately forty-five degrees with the plane of said link member, said edge extending between a point to one side of said link member and a point to the opposite side of said median plane, said edge defining the entire transverse cutting extent of the cutter, said two points lying in two respective planes substantially parallel with the plane of said link member, and means confined between said two planes securing said elements to said link member.

5. A cutter link means as defined in claim 4, wherein said securing means is integrally secured at one end to said leading cutting edge element adjacent the first mentioned point and extends therefrom toward said median plane and is integrally secured at its opposite end to said link member.

References Cited in the file of this patent UNITED STATES PATENTS 661,021 Pratt Oct. 30, 1900 2,508,784 Cox May 23, 1950 2,589,914 Wolf Mar. 18, 1952 2,631,460 Transeau Mar. 17, 1953 2,632,484 Merz Mar. 24, 1953 2,652,076 Bye Sept. 15, 1953 2,655,958 Gommel Oct. 20, 1953 2,725,083 Ackley Nov. 29, 1955 2,730,143 Ryde Jan. 10, 1956 

